1. Field of the Invention
The present invention relates generally to electromagnetic actuators and, more specifically, to electromagnetic actuators having an armature linkage movable between two stable positions either manually or through the application of an appropriate electrical pulse.
2. Description of the Prior Art
The present invention is an improvement over U.S. Pat. No. 4,072,918 to R. A. Read, Jr., issued Feb. 7, 1978. That patent discloses a bi-stable electromagnetic actuator which, like all electromagnetic actuators, converts electrical pulses into mechanical action. Specifically, the actuator disclosed includes an armature and a linkage which transmits the mechanical action of the armature. The armature and linkage move between two locations and a permanent magnet maintains the armature at one location, thereby reducing the power consumption of the actuator. In addition, the actuator includes a coil which, upon application of an appropriate pulse, reduces the net flux through the armature and allows a spring to overcome the resulting reduced magnetic force and thereby to move the armature and the linkage. The armature moves in one direction in response to the force exerted by the spring, and in the opposite direction in response to either a force applied manually to the linkage or by a magnetic force applied by the actuator coil.
Many applications require that this type of actuator allow the user to manually advance the linkage in the direction in which the spring would advance the armature upon actuation, without application of an electrical impulse to the coil. Thus, as an initial consideration, the linkage should be movable apart from the armature. In addition, in instances where the armature moves the linkage, it should engage the linkage without any "hammering" action which may damage the parts and/or produce metallic debris.
The bi-stable electromagnetic actuator of the present invention allows a user to manually control the armature linkage and move it from one location to another while the armature is held in one position by the permanent magnet. It also produces smooth, mechanical action when actuated by an electrical impulse. The actuator of the present invention provides a construction which minimizes the expense of manufacture and assembly and gives precise, uniform and reliable performance.